The engine is a power machine capable of converting other forms of energy into mechanical energy, including e.g. internal combustion engine. The internal combustion engine, a typical engine, is a heat engine in which a fuel is combusted inside the machine and thermal energy emitted thereby is directly converted to power. Among common internal combustion engines, piston internal combustion engines are the most prevalent. In the piston internal combustion engine, due to reciprocation of a piston, the piston generates a reciprocating inertia force and an inertia moment, and the above inertia force and inertia moment are quite unbalanced, accompanied with the defect of having great noise in operation. In the piston internal combustion engine, inertial rotation is realized by a flywheel, but the flywheel still cannot solve the above problem of non-uniform torque output, thus resulting in ineffective power conversion, all of which seriously restrict an operation speed thereof.